Conventionally, there is a method of reducing the distortion or the like of a projected image by capturing a projected image projected onto a projected surface by a projector, by a camera, performing geometric correction or the like to an image to be projected with the captured image. In a case where this method is used, a corresponding point between the projected image projected by the projector and the captured image acquired by the camera (namely, a corresponding point in pixel between the projector and the camera) is necessary to detect previously. Various methods have been considered as a method of detecting the corresponding point and, for example, a phase-shift method has been considered (e.g., refer to Non-Patent Document 1).